Property Behaviors and Swift 4.0 Stage 1.

Wallacy · January 18, 2017, 6:55pm

Is Property Behaviors considered for Stage 1?

apple/swift-evolution/blob/master/proposals/0030-property-behavior-decls.md

# Property Behaviors

* Proposal: [SE-0030](0030-property-behavior-decls.md)
* Author: [Joe Groff](https://github.com/jckarter)
* Review Manager: [Doug Gregor](https://github.com/DougGregor)
* Status: **Deferred**
* Decision Notes: [Rationale](https://lists.swift.org/pipermail/swift-evolution-announce/2016-February/000047.html)

## Introduction

There are property implementation patterns that come up repeatedly.
Rather than hardcode a fixed set of patterns into the compiler,
we should provide a general "property behavior" mechanism to allow
these patterns to be defined as libraries.

[Swift Evolution Discussion](https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151214/003148.html)<br/>
[Review](https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160208/009603.html)

## Motivation

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Because the project roadmap says:

The high-priority features supporting Stage 1's source and ABI stability
goals are:
...
Resilience: resilience provides a way for public APIs to evolve over time,
while maintaining a stable ABI. For example, resilience eliminates the fragile
base class problem <https://en.wikipedia.org/wiki/Fragile_base_class> that
occurs in some object-oriented languages (e.g., C++) by describing the
types of API changes that can be made without breaking ABI (e.g., "a new
stored property or method can be added to a class").
...

And i think this feature will help with that. Not a complete solution for
resilience problem, but "provides a way for public APIs to evolve over time
".

Thanks.